This project addresses the adaptive evolution of visual signals and the pigments involved in color vision, in Panamanian marine fishes. There are over on hundred pairs of sister species of fishes with representatives on either side of the Isthmus of Panama. Water on the Pacific side suffers more spectral attenuation than on the Caribbean side, particularly at shorter (blue) wavelengths. The system thus permits multiple comparisons of the effect of a single, broad selective agent on the evolution of a communication system. Spectral attenuation functions will be characterized in the two environments. The reflectance functions of color patterns and the absorption spectra of short-wavelength sensitive (SWS) opsins will be determined for 20 species pairs. SWS opsins will be sequenced in each species pair. We will then test for adaptation to differences in the visual environments and for convergent evolution at the phenotypic and molecular levels. Sequencing and functional characterization of opsins can provide valuable insight into the molecular basis of genetic disorders of vision.